Method of Correcting a Multi-Feed in an Automatic Document Feeder

ABSTRACT

A method for operating a paper feed system for use in a printing apparatus that detects multi-feeds and separates all sheets while allowing a single sheet to continue is disclosed. The separation method controls a motor for the separator roller that can be torque controlled, allowing varying torques depending on media type and/or user input. The separation method detects multi-feeds, correct the multi-feed, and ultimately feeds one sheet at a time through the automatic document feeder.

CROSS REFERENCES TO RELATED APPLICATIONS

This patent application is related to the U.S. patent application Ser.No. ______, entitled “Automatic Document Feeder Multi-Feed Corrector,”which is filed contemporaneously herewith and assigned to the assigneeof the present application.

BACKGROUND 1. Field of the Invention

This invention relates generally to an automatic document feeder for ascanner in an image forming apparatus, and more particularly, to aseparation system that uses a motor for the separator roller. The motormay be torque controlled to allow varying torques depending on mediatype and/or user input. It can also allow the separation system todetect multi-feeds, correct the multi-feeds, and ultimately feed onesheet at a time through the automatic document feeder for the scanner.

2. Description of the Related Art

Multi-feeds are a problem when separating and feeding sheets to ascanner in an image forming device. A multi-feed occurs when two or moresheets are fed at once and can cause several problems. Typically, amulti-feed will jam somewhere in a machine. However, if the sheets passthrough the machine without jamming, the user may find blank sheetswithin large print runs, or, in the case of duplex printing, blanksides. Reducing the number of multi-feeds experienced will improve theoverall user experience. Multiple solutions have been advanced fordetecting and separating multi-feeds.

United States Pat. App. No. 2012/0306147 discloses a multi-feeddetection and correction system. It is a feed system used for a printerthat includes a reversing roller driven by a motor. However, theadvantage of the invention disclosed here is that the motor is torquecontrolled and thus allows varying torque to help separate the media.Without this torque control, the reversing roller may slip on the media,and not reverse the multi-fed sheets.

There is still a need for a multi-feed system that will facilitatedetection and separation of sheets while reliably feeding sheets one ata time.

SUMMARY OF THE INVENTION

An automatic document feeder (ADF) for a scanner generally has a pickand separation system to ensure the proper picking of only one sheet ata time to be imaged. The pick and separation system feeds the sheet tothe feed rollers that control the media position and speed of movementthrough the imaging area. The pick roller initiates the pick process andfeeds one or more sheets of an input stack to the separation system.

In one embodiment of the separation system design, a driving feed beltmated with a counter-rotating separator roller is used. The pick rollerand feed belt are rotated in the process direction. The separator rolleris counter-rotated to prevent multiple sheets from feeding but torquecontrolled to allow one sheet to successfully feed. The torque can becontrolled using various types of slip clutches or magnetic clutches.However, here, a motor is used to control the torque. The motor has anadvantage over the clutches in that it will last the life of theproduct. Another advantage is that a motor allows the torque to bemodified without changing hardware.

Media sheets may stick together when picked and fed together through theADF. When two or more sheets are fed together, it is generally calledmulti-feeding. There are numerous separation mechanisms used that helpprevent multi-feeds. For a scanner ADF, however, the input media may notbe pristine; rather, it may have folds, wrinkles, creases, and/or havevarying friction characteristics between the input sheets. Therefore, itis possible, and, in-fact common, for multi-feeds to occur in scannerADFs.

Multi-feeds result in a loss of data, so it is desirable to have onlyone input sheet fed through a scanner at a time. If the ADF does nothave a sensor to detect two or more sheets feeding together, then theadditional sheets or sheets may be simply fed through the device withoutscanning or copying.

Scanner ADFs may detect multi-feeds in different way, such as by usingan ultra-sonic or optical sensors. These sensors alert the user that amulti-feed has occurred, so the scanning job may be suspended orstopped, and thus prevent the loss of data when scanning. The user must,however, open the image forming device and remove the multiple sheetsbefore continuing.

The invention described herein is a separation system that uses a motorfor the separator roller. This motor may be torque controlled to yieldvarying torques depending on media type and/or user input. The motor canalso allow the separation system to detect multi-feeds, correct themulti-feed, and ultimately feed one sheet at a time through the ADF. Inone embodiment, a single motor drives the feed belt. The motor anddriven feed belt move the sheets in the process direction. A secondmotor controls the separator roller that separates the multi-fed sheets.By controlling the motor current and duty cycle, the separator motortorque is controlled, which results in a counter-rotating torque appliedto the separator roller.

In normal operation, the separator motor imparts a torque to theseparator roller that allows one sheet to be fed successfully by thefeed belt. If multiple sheets enter the feed belt/separator roller nip,then the friction between the bottom sheet and the separator rollerwould be sufficient to overcome the torque and reverses the direction ofthe bottom sheet or bottom sheets.

In the case where the friction between the sheets is large enough toovercome the separator torque, the multiple sheets will feed past thisnip to the multi-feed sensor. The multi-feed sensor, ultra-sonic orother, will detect the multiple sheets and begin the correction process.At this point, the feed motor is stopped, while the separator motorcontinues to drive the bottom sheet or bottom sheets backward, whileincreasing the torque value until the multi-feed sensor detects only onesheet. The feed belt motor then resumes operation, and moves the singlesheet of media in the process direction.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIG. 1 shows the schematic layout of the ADF pick and separation system.

FIG. 2 shows the ADF pick and separation system.

FIG. 3 shows the ADF separator motor and roller with the with the feedbelt and pick assembly removed.

FIG. 4 shows the ADF separation system with an ultrasonic multi-feedsensor.

FIG. 5 shows the multi-feed correction process.

FIG. 6 shows a printer with an automatic document feeder (“ADF”).

DETAILED DESCRIPTION

It is to be understood that the present disclosure is not limited in itsapplication to the details of construction and the arrangement ofcomponents set forth in the following description or illustrated in thedrawings. The present disclosure is capable of other embodiments and ofbeing practiced or of being carried out in various ways. Also, it is tobe understood that the phraseology and terminology used herein is forthe purpose of description and should not be regarded as limiting. Asused herein, the terms “having,” “containing,” “including,”“comprising,” and the like are open ended terms that indicate thepresence of stated elements or features, but do not preclude additionalelements or features. The articles “a,” “an,” and “the” are intended toinclude the plural as well as the singular, unless the context clearlyindicates otherwise. The use of “including,” “comprising,” or “having”and variations thereof herein is meant to encompass the items listedthereafter and equivalents thereof as well as additional items. Termssuch as “about” and the like are used to describe variouscharacteristics of an object, and such terms have their ordinary andcustomary meaning to persons of ordinary skill in the pertinent art.

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments of the invention are shown. Indeed, the invention may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements Like numerals refer to like elements throughout the views.

Referring initially to FIG. 1, the ADF layout is shown, which operatesinside a printer 601 (see FIG. 6). The pick tire 101 and feed belt 111are driven by the pick motor (not shown in this figure) and move themedia in the process direction 121 shown. The separator roller 131 isdriven in the opposite direction by the separator motor (not shown inthis figure).

Referring now to FIG. 2, the separator motor 201 and the pick motor 211are depicted. The separator motor 201 is current controlled to provide aspecific torque value. Because motor torque is proportional to motorcurrent, by controlling the current through the separator motor, theproper counter-rotating torque is achieved at the separator roller 131.The motor current is controlled by adjusting the command signals to themotor driver.

I _(M) =G _(MD) *V _(REF)

-   -   I_(M): Motor Current (Amp)    -   G_(MD): Motor Driver Gain    -   V_(REF): Reference Voltage (Volt)

T _(M) =K _(T)*(I _(M) −I _(NL))

-   -   T_(M): Motor Torque (mN−m)    -   K_(T): Motor Torque Constant (mN−m/Amp)    -   I_(NL): Motor No Load Current (Amp)

FIG. 3 shows the separator roller 131 and motor 201 with the feed belt111 and pick assembly 221 removed. Since the reference voltage is avalue that can be change through the scanner firmware, the torque valueat the separator roller 131 can be changed, allowing different torquesettings for different media scanned. The torque on the separator rollercould also be changed by the user depending on the media used.

A multi-feed sensor 421 is shown in FIG. 4. For the multi-feeds thatpass the feed/separation system, the ADF has a two-part sensor toidentify this situation. This two-part ultrasonic sensor 421 that isdownstream of the feed belt/separator roller has an ultrasonictransmitter 401 and an ultrasonic receiver 411. Alternatively, anoptical or infrared sensor may be used to provide the same function asthe ultrasonic sensor shown here. The ultrasonic sensor detects when twoor more sheets are present due to the air gap between sheets thatmuffles the sound of the transmitter.

FIG. 5 shows the multi-feed correction process where the separationmotor torque is increased to prevent the multi-feed from advancing.During normal operation, a user initiates a scan request 501 and atleast one media page advances to the multi-feed sensor 511. If themulti-feed sensor does not detect a multi-feed, then the media pageadvances through the ADF 522 to completion 523. If a multi-feed isdetected 521, i.e., two or more sheets are present in the path, then thepick motor is stopped 525. Thus, the driving force on the multiplesheets would stop. The separator motor torque is increased in gradualincrements, for example 5% 530, to provide additional separating torque.The media interval is then viewed 535 and the multi-feed sensor queriedto determine if the multi-feed is clear 540. If the multi-feed iscleared, then the separator motor torque is reset to its default value545, and feeding is resumed. If not, then unless the maximum separatormotor torque has been reached 550, then the separator motor torque isincreased 530. The separator motor torque is increased in gradual stepsuntil the bottom sheet(s) reverse direction and the multi-feed sensor421 reports that a single sheet is present. The pick motor wouldrestart, and the normal feed and separation process would resume. If themaximum separator motor torque is reached 550, and the multi-feed is notcleared, then multi-feed jam is declared 575, requiring userintervention.

It is also possible during the separation process that the separatorroller 131 is slipping on the bottom sheet and spinning in reverse. Inthis case, the multi-feed sensor 421 is monitored, and if there is nochange in the status within a certain time period, then the speed of theseparator roller 131 is reduced, while increasing the torque. Theprocess would continue until the multi-feed sensor 421 reports a singlesheet is present. The pick motor 211 then restarts, and the normal feedand separation process would resume.

The foregoing description of several embodiments of the invention hasbeen presented for purposes of illustration. It is not intended to beexhaustive or to limit the invention to the precise forms disclosed, andobviously many modifications and variations are possible in light of theabove teaching. It is intended that the scope of the invention bedefined by the claims appended hereto.

We claim:
 1. A method of separating multi-feeds in an automatic documentfeeder, comprising: initiating a scan request so that at least one mediapage advances to the multi-feed sensor; stopping the pick motor if amulti-feed is detected; increasing the separator motor torque in gradualincrements, to provide additional separating torque; determining if themulti-feed is clear; restarting pick motor if the multi-feed is clear;resuming normal feed and separation process.
 2. The method of claim 1,wherein the sensor is ultra-sonic.
 3. The method of claim 1, wherein thesensor is optical.
 4. The method of claim 1, wherein a driving feed beltmated with a counter-rotating separator roller is used, and theseparator roller is counter-rotated to prevent multiple sheets fromfeeding.
 5. The method of claim 4, wherein the separator roller istorque controlled with a motor.